This page contains detailed protocols for the experiments in ‘Colour biases in learned foraging preferences in Trinidadian guppies’. For this project, we wanted to determine whether object preferences were plastic without constraint for both green and blue objects in Trinidadian guppies. Given these colours differ in their foraging relevancy for guppies we wanted to determine whether the shift in preference would be unconstrained.
Our protocol aimed to manipulate object preferences for the green and blue objects (Figure 2) of individual guppies by manipulating their foraging experiences with these objects. This was done by providing food reinforcement for approaching one of the two colours.
On the first trial, guppies were placed in the test tank with both objects but empty food strips to measure preferences at a baseline. Training then occurred once daily between 10h00 to 16h00 for 20 days constituting 20 trials. During training, the location of the rewarding object (left or right) was randomized across days and individuals. That is, only the object’s appearance provided a reliable cue to food location. On the 21st day, an unreinforced ‘probe’ test was given where new duplicates of the objects were presented with empty plastic strips attached to them. This unreinforced trial (trial 21) was used to assess whether learning had occurred. In experiment 2 an additional four test trials were conducted to see how robust learning was in both groups across different contexts.
Figure 1: An experimental timeline representing the order of the trials. Experiment 1 ends at trial 21. Experiment 2 ends at trial 29.
For the initial and final tests (Probe 1, Probe 2, G1, G2, and Odour) guppies were presented with the green and blue objects with empty food strips attached to them. You can see an example of this above. The following protocol was used for testing:
Guppies were rewarded for either foraging from either the blue object or the green object, forming the two experimental treatments, blue-rewarded and green-rewarded. The food reward was a gelatin mixture of flake food which was placed on the back of the objects facing away from the guppy so that the rewarding object had to be approached and investigated for the food reward to be discovered. The protocol was as follows:
The food strips that were attached to the objects were made with the following protocol:
Figure 2: (A) The two objects used in experiment 1. Blue-trained guppies were trained to the left object and green-trained guppies were trained to the right object. The manufacturer’s colour name for the blue object is ‘dark azur (hex #078BC9) and for the green object is ‘bright yellowish green’ (hex # BBE90B). (B) The 7 pairs of objects in experiment 2. The numbered object pairs are used for training while the lettered object pairs are used for testing. The experimental timeline represents the order of the trials. Experiment 1 ends at trial 21.
The colours used in the experiment are listed in Table 1.
| Object Colour | Colour Family | Exact Colour | Hex Value |
|---|---|---|---|
| Green | Dark Green | Bright Yellowish Green | BBE90B |
| Green | Dark Green | Dark Green | 237841 |
| Blue | Blue | Dark Azur | 078BC9 |
| Blue | Blue | Bright blue | 0055BF |
The objects were 6 pairs of Lego blocks with the manufacturer colours A and B. The specific models for the object pairs are listed in Table 2. As of 2021, these bricks can be looked up and/or purchased using the official Lego store’s Choose a brick service by entering the design ID in the Enter an item number or design ID prompt of the Enter set number section.
| Object Pair | Brick Style | Design ID |
|---|---|---|
| Pair A | BRICK 1X2 | 3004 |
| Pair B | BRICK 2x4 | 3001 |
| Pair 1 | BRICK 1X2 (x2) | 3004 |
| Pair 2 | BRICK 2X4 | 3001 |
| Pair 3 | BRICK 2X2 | 30165 |
| Pair 4 | BRICK 1X1 | 3005 |